JPH03251734A - Material tester of proportional-plus-integral control system - Google Patents

Abstract

PURPOSE:To enable employment of an integrating circuit of a proportional-plus-integral control for valve neutral compensation as well by a method wherein a deviation 0 is detected by a hold instruction circuit, an integrated value thereof is held and added to a deviation signal constantly and thereby execution of the valve neutral compensation is enabled. CONSTITUTION:On the occasion of a proportional-plus-integral control, an integrated value obtained by a driving control device 33 is added, as it is, to a deviation and thereby a servovalve 11 is driven. On the occasion of valve neutral compensation, a displacement pattern of 0 level is generated from a waveform generating device 21. At this time, it sometimes happens on the occasion of the valve neutral compensation that a load actuator 12 is driven and a feedback value shows a prescribed value, even when an input current of the servovalve 11 is zero. In this case, the deviation of the feedback signal from the displacement pattern of 0 level is integrated and a corrective current corresponding to an integrated value thus obtained is supplied to the servovalve 11. Then stability is attained when a deviation value is zero. This deviation of zero is detected by a hold instruction circuit 34 and an integrated value thereof is held and added to the deviation value constantly. By this method, execution of the valve neutral compensation is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a material testing machine that drives a load actuator by proportional-integral control of a servo valve based on a load pattern signal and a feedback signal.

B. Prior art FIG. 3 is an overall configuration diagram showing a conventionally known material testing machine of this kind using a proportional-integral control system.

In the figure, a test machine main body 10 includes a hydraulic actuator 12 that is driven and controlled by a servo valve 11 and loads the specimen SP, and a load cell 13 and a displacement meter 14 that detect the load and displacement amount generated on the specimen SP.

On the other hand, 21 is a waveform generation circuit that generates a waveform signal according to the load pattern applied to the specimen SP, 22A is a load amplifier that amplifies the detection output of the load cell 13, and 22B is a stroke that amplifies the detection output of the displacement meter 14. Amplifier, 2
3 is a drive control circuit that generates an input signal for the servo valve 11 by performing proportional-integral calculations based on the load pattern signal from the waveform generation circuit 21 and the feedback signal from the amplifier 22A or 22B selected by the switch 24; be.

The drive control circuit 23 includes a deviation device 231 that calculates the deviation between the load pattern signal and the feedback signal, an amplifier 232 that amplifies the signal representing the deviation and outputs the deviation signal El which is a proportional term, and a deviation signal E1. An analog integration circuit 233 that integrates and outputs an analog signal E2 indicating an integral term.
, an adder 234 that adds the signals El and E2 of the proportional term and the integral term, and a servo amplifier 23 that amplifies the output E2 of the adder 234 to form the input signal i of the servo valve 11.
It consists of 5.

Furthermore, 25 is a manually operated volume for compensating the valve neutral, and its offset voltage E
3 is added to adder 234. Here, when the input current supplied to the servo valve 11 is zero, the deviation device 2
Since the output E1 of the actuator 31 is zero, the actuator 12 should originally be held at the current position.

However, due to the influence of oil temperature and hydraulic conditions or changes over time of the servo valve 11, the servo valve 11 completely shuts off fluid such as oil even when the input current i is zero. A correction current 10 is applied to the valve 11 so that the servo valve 11 is in a true neutral position.

C0 Problems to be Solved by the Invention As is well known, static tests and dynamic tests are performed in such a material testing machine, and in general, the integration circuit 233 is used during static tests.
However, since the automatic gain control method is adopted during the dynamic test, the integrating circuit 233 is not used. Therefore, during a static test, a correction similar to the valve neutral compensation is necessarily applied using the integral term without applying the offset voltage E3 by the volume 25, but during a dynamic test, the correction using the volume 25 is performed because the integral term does not apply the correction. is necessary. Therefore, in this type of material testing machine, the volume 25 for the purpose of valve neutral compensation and the analog integration circuit 233 for the purpose of accuracy compensation of feedback control are essential, and the circuit configuration becomes complicated.

A technical object of the present invention is to realize valve neutral compensation and improvement in accuracy of feedback control with a simple circuit configuration.

The present invention will be explained in conjunction with FIG. 1 showing an embodiment of the present invention.The present invention includes a waveform generating means 21 that outputs a pattern waveform that loads the specimen SP, and a servo valve 11. a load actuator 12 that is controlled by and loads the specimen SP;
A detection means 13.14 detects a change in physical quantity due to deformation of the specimen SP, and a proportional-integral calculation is performed based on a signal indicating a change in the detected physical quantity and a signal indicating a load pattern to drive the servo valve 11. The present invention is applied to a proportional-integral control type materials testing machine having a drive control means 33 that generates a signal.

A hold circuit 3 holds the obtained integral value.
35 is provided in the drive control means 33, and a hold command circuit 3 holds the integral value when the deviation is zero.
4, the above-mentioned technical problem is achieved.

During the zero action proportional integral control, the integral value obtained by the drive control means 33 is directly added to the deviation to drive the servo valve 11. During valve neutral compensation, the waveform generating means 21
A displacement pattern of O level is generated. At that time, even if the input current to the servo valve 11 is zero before valve neutral compensation, the load actuator 12 is driven.
The feedback signal may indicate a predetermined value. Therefore, in this case, if the deviation between this feedback signal and the O level displacement pattern is integrated and a correction current corresponding to the integrated value is supplied to the servo valve 11, the deviation becomes zero and becomes stable. If this zero deviation is detected by the hold command circuit 34 and the integral value at this time is held and constantly added to the deviation signal, valve neutral compensation becomes possible.

The integral circuit for proportional-integral control can also be used for valve neutral compensation.

It should be noted that in the above-mentioned sections and section E, which describe the present invention in detail, figures of embodiments are used in order to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Embodiment FIG. 1 is an overall block diagram showing an embodiment of the present invention, and the same parts as in FIG. 3 are given the same symbols, and the explanation will focus on the differences.

In the figure, 33 is a drive control circuit that forms the input current i of the servo valve 11, which includes a deviation device 331 that calculates the deviation E1 between the load pattern and the feedback signal, an amplifier 332 for the deviation signal E1, and an amplifier 332 for the deviation signal E1. an amplification/clipping circuit 333 that gives a gain to the deviation signal E1 to determine an integration time constant and limits upper and lower limits; and a voltage/frequency conversion circuit (V/ F converter) 334,
an up/down counter 335 that counts the output pulse signal of the V/F converter 334; and a polarity determination circuit 336 that determines the polarity of the output voltage of the clip circuit 333 and controls whether the up/down counter 335 counts up or down. and has. Furthermore, counter 3
The digital integral value output from 35 is converted into an analog integral signal E.
an analog/digital conversion circuit (D/A converter) 337 that converts the D/A converter 337 into an analog/digital converter 337, and an adder 338 that adds the analog integral signal E2 of the D/A converter 337 and the deviation signal E1.
and a servo amplifier 339 that amplifies the output ε2 of the adder 338 and outputs the input current i.

Furthermore, 34 is a control circuit consisting of a microcomputer or the like, which causes the waveform generation circuit 21 to generate a load pattern according to test conditions manually entered from a control panel (not shown). In addition, RUN is applied to the up/down counter 335.
The /HOLD signal is sent to control whether to continue the counting operation, that is, the integral operation, or to hold and output the integral value, and the WRIGHT/READ signal is sent to set the up/down counter 335 to a predetermined value. or read the integral value. Furthermore, the control circuit 34
is the switch 24 when performing valve neutral compensation.
is switched to the contact side and the deviation E1 is read. Here, the hold command for valve neutral compensation is the second
This can be done automatically by the procedure shown in the figure.

That is, in step S1, it is determined whether the test is a dynamic test or a static test, and in the case of a static test, the process proceeds to step S6 to start the test, and in the case of a dynamic test, the process proceeds to step S2. In step S2, the switch 24 is switched to the contact position to select the stroke amplifier 22A, and in step S3, a 0-level load pattern is applied from the waveform generation circuit 21.

At this time, when the deviation signal is on the + side, the counter 335 counts up, and the count value is added to the adder 338 as an analog integral signal E2 by the D/A converter 337, and added to the deviation signal E1. As a result, the input current i of the servo valve 11 increases to the + side, and by driving the servo valve 11 to the + side, the actuator 12
The displacement of is increased to the + side. In other words, since the amount of feedback increases on the positive side, the deviation approaches zero in the operation of the entire control system. When the deviation signal is on one side, the counter 335 counts down, and the count value is D/
In the A converter 337, it is applied as an analog integrated signal E2 to an adder 338, where it is added to the deviation signal E1. As a result, the input current i of the servo valve 11 increases to one side,
By driving the servo valve 11 to one side, the displacement of the actuator 12 is increased to one side. In other words, since the amount of feedback increases to one side, the deviation approaches zero in the operation of the entire control system.

Before the valve neutral is compensated, the deviation signal does not indicate zero but indicates an offset value, so the count value of the up/down counter 335 becomes a value corresponding to the offset value. Therefore, when the count value reaches a value corresponding to the offset current of the servo valve 11, the deviation signal E1
is almost zero. Therefore, in step S4, the deviation signal E
Determine whether 1 is almost zero, and if it is almost zero, step S5
Instructs the counter 335 to hold. As a result, an offset voltage E2 corresponding to the offset current of the servo valve 11 is supplied to the adder 338. The test is then started in step S6. In this way, valve neutral compensation is automatically performed in the early cycles of the dynamic test.

On the other hand, during a static test, the test is started from step S1 without doing anything, so the counter 335 is not held, and the count value is used for calculating the integral term of proportional-integral control.

In this way, in the embodiment shown in FIGS. 1 and 2, the material testing machine is driven by the proportional-integral control method during static testing, and the counter 335 used for proportional-integral control is controlled during dynamic testing. Since the value is automatically held and valve neutral compensation is performed, there is no need for a volume like in the past, and a simple circuit configuration is created that serves as both a valve neutral compensation circuit and an integral circuit.

Further, the READ signal from the control circuit 34 is sent to the counter 335.
By reading the count value when valve neutral compensation is performed by supplying the voltage to Furthermore, if you read the value held by the counter 335 at the end of the test and store it with battery backup, you can send the WRIGHT signal to the counter without having to repeat the above-mentioned valve neutral compensation procedure each time prior to the dynamic test. It is also possible to initialize it to 335, which improves work efficiency.

Note that in the above, a digital integration circuit using a V/F converter and an up/down counter was used.

A configuration may also be adopted in which a hold circuit is provided at the output stage of the analog integration circuit to hold an input signal in response to a command from a microcomputer, and the output is added to the deviation signal.

In the configuration of the above embodiment, the waveform generating circuit 21 serves as a waveform generating means, the displacement meter 14 and load cell 13 serve as a detecting means, the drive control circuit 33 serves as a drive control means, and the counter 335 serves as a drive control means.
constitutes an integrating circuit and a hold circuit, and the control circuit 34 constitutes a hold command circuit, respectively.

As described in detail of the G1 invention, according to the present invention, the integral circuit for proportional-integral control and the valve neutral compensation circuit can be used together, and the control system of a material testing machine using proportional-integral control can be simplified.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram showing one embodiment of the present invention, and FIG.
The figure is a flowchart showing an example of the procedure of the present invention, and FIG. 3 is a diagram showing the overall configuration of a conventional material testing machine. 10: Testing machine body 11: Servo valve 12
: Hydraulic actuator 13: Load cell 14: Displacement meter 21 = Waveform generation circuit 33: Drive control circuit 331: Deviation device 334: V/F converter

Claims (1)

[Claims] 1) a waveform generating means that outputs a pattern waveform that loads the specimen, a load actuator that is controlled by a servo valve and loads the specimen, a detection means that detects a change in a physical quantity due to deformation of the specimen, and the detection means. a proportional-integral control method material testing machine, comprising: a drive control means for performing proportional-integral calculations based on a signal representing a change in the physical quantity and a signal representing the load pattern to generate a signal for driving the servo valve; , wherein the drive control means includes a hold circuit that holds the obtained integral value, and further includes a hold command circuit that holds the integral value when the deviation is zero. Machine.